This disclosure relates generally to fault-detection and fault-isolation techniques for electronic equipment and, more particularly, to a technique for detecting and isolating faults or defects related to the operation of a power supply in a personal computer system.
Computer systems in general and personal computer systems in particular have attained widespread use within many segments of today""s society, and may be viewed as information handling systems that afford independent computing power to one user or to a plurality of users. A personal computer system can conveniently be classified as a desktop, floor standing, or portable microcomputer.
A personal computer system will likely include one or a plurality of peripheral devices that are coupled to the system processor and that perform specialized functions. Examples of peripheral devices include modems, sound and video devices or specialized communication devices. Mass storage devices such as hard disks, CD-ROM drives and magneto-optical drives are also considered peripheral devices.
FIG. 3 is a block diagram of an exemplary computer system 300. The computer system depicted in FIG. 3 is seen to include a microcomputer that includes a microprocessor (or simply xe2x80x9cprocessorxe2x80x9d) 310, associated main memory 350 and control logic and a number of peripheral devices 330, 387, 391 that provide input and output for the system 300. A typical computer system 300 includes a power supply 110 connected to a voltage regulator 315 providing power to the processor 310. Peripheral devices shown in FIG. 3 include keyboards 391, graphics devices 330, and traditional I/O devices 387 that often include display monitors, mouse-type input devices, floppy and hard disk drives, CD-ROM drives and printers.
The number and kinds of peripheral devices that are appended to personal computers continue to expand. For example, many computer systems also include network capability, terminal devices, modems, televisions, sound devices, voice recognition devices, electronic pen devices, and mass storage devices such as tape drives, CD-R drives or DVDs. The peripheral devices usually communicate with the processor over one or more buses 320, 360, 380, with the buses communicating with each other through the use of one or more bridges 340 and 370.
One skilled in the art will recognize that the foregoing components and devices are used as examples for sake of conceptual clarity and that various configuration modifications are common. For example, the processor 310 is used as an exemplar of any general processing unit, including but not limited to multiprocessor units; host bus 320 is used as an exemplar of any processing bus, including but not limited to multiprocessor buses; and host-to-PCI bridge 340 and PCI-to-ISA bridge 370 are used as exemplars of any type of bridge.
PC systems typically include a system board to interconnect system components and peripheral devices and include a power supply to provide specified DC output voltages to system components and peripherals. For example, the power supply in a desktop computer typically converts 110 volts AC to various DC voltages that are distributed to PC subsystems and peripherals. Typically, 3.3 VDC may be provided to a modem, 5.0 VDC to a hard drive, and 12.0 VDC to a CD-ROM drive. FIG. 2 is a rendition, in block diagram form, of a conventional power supply system 200, such as may readily be used with PC systems. Power supply 110 converts a nominal 110-volt AC input at terminals 220 and 221 to a plurality of DC voltage outputs at terminals 230, 240 and 250. Power supply 110 incorporates a self-test procedure that is initiated when a predetermined signal is applied to an input terminal 160. In practice, the required signal may appear between terminal 160 and system ground (GND) 180. In general, if the self-test procedure indicates that the power supply performance complies with predetermined criteria, an appropriate signal indicating such compliance is caused to appear at output terminal 150.
Specifically, it is common that commercially available power supply systems undertake the self-test function during the PC start-up process. The self-test procedure is often initiated by applying a predetermined voltage to a Power Supply Enable (PSE) input, or the equivalent, on the power supply. In one embodiment, the necessary voltage may be, for example, a logic-level ZERO. Power supply self-test is largely defined by the operation of a fault detector in the power supply. For the purposes of this Description, it may be assumed that the fault detector measures each of the power supply output voltages to determine whether those voltages reside within respective specified predetermined ranges, xc2x15% being commonplace. If the observed output voltages comply with this specification, then the fault detector will issue an affirmation that no fault exists within the power supply. The affirmation may take the form of a logic-level ZERO at the output of the fault detector, but other prescribed outputs may be encountered. The output of the fault detector is routed from the power supply through a connector to the PC system board. This signal, which may be colloquially referred to as the PS Good (PSG) output of the power supply, is then used to drive an indicator, usually a light-emitting diode (LED). Power supplies that operate generally as described above are commercially available from Lite-On Electronics, Inc., Milpitas, Calif. (Model #PS-520-7D), and from Delta Electronics, Taipei, Taiwan (Model # NPS-200PB-73). Activation of the LED serves as an indication that the power supply is operating, as is the entire PC. Conversely, failure of the LED to light may justify an inference that the power supply, or some other aspect of the PC, is not operative.
However, failure of the LED indicator to light cannot be conclusively taken as confirmation that the power supply is itself defective. The ambiguity derives from an existing PC design in which the PSE input to the power supply is generally contingent on the combination of a number of inputs to logic circuitry that generates the PSE signal. Simply, a power-supply-enabling PSE input becomes available only when the PC ON/OFF control has been activated, and when selected other PC components, subsystems, or peripherals have been determined to be operating properly. Therefore, failure of the LED indicator to light may be taken to indicate a fault or defect, but does not serve to specifically localize the defect. This uncertainty is, of course, an impediment to a troubleshooting and repair process. Clearly, if a defect could be confidently isolated to the power supply, then a malfunctioning PC could be returned to operation simply be replacing a defective power supply. On the other hand, if the fault is not able to be localized to the power supply, the entire PC may need to be taken out of service for repair, perhaps for an unnecessarily extensive duration.
Accordingly, what is desired is a simple, expedient and effective mechanism for isolating faults in a PC. Specifically, the mechanism should confidently determine whether the cause of an inoperative PC resides within the PC power supply or may be found elsewhere. Currently, a user has no means to accurately determine when a power supply system has failed. An indicator associated with the self-test function may respond indiscriminately to the failure of a power supply or, alternatively, to the grounding of the system board due to unrelated causes. When a power supply system fails, the user (or a repair technician) must isolate each component from the circuit and connect each component to the indicator using a jumper or other connector. Only after a repair technician isolates and tests the power supply can the repair technician determine whether failure of the indicator to illuminate, or otherwise provide an affirmative indication, is due to a fault in the power supply or a fault in the system board.
Accordingly, aspects of the disclosure allow a user or repair technician to immediately and accurately distinguish between the failure of a power supply and a failure of a system board. In addition, a user or repair technician may initiate self-test of a power supply and to observe an indicator to determine if a power supply has failed. The above advantages allow the user or repair technician to identify the failure of a power supply without having to transport the computer system to a repair facility. Other advantages allow a user to determine whether a power supply has failed without removing a computer casing or otherwise disassembling the computer. Efficient discrimination between the failure of a power supply and the failure of the system board allows a user or repair technician to immediately identify the necessary replacement components, and to reduce the need for separately dispatching repair parts.
The above and other objects, advantages and capabilities are achieved in one aspect of the disclosure in a testing method for a personal computer that incorporates (i) and ON/OFF control, (ii) a power supply having a fault detector, a PSE input, and a PSG output coupled to the fault detector, (iii) an enabling circuit having a plurality of inputs, at least one of which is coupled to the ON/OFF control, the enabling circuit for providing an enabling signal at the PSE input of the power supply, and (iv) an indicator coupled to the PSG output. The method comprises engaging the ON/OFF control, observing the indicator, and if the indicator does not provide a positive indication, simulating an enabling signal at the PSE input of the power supply.
In another aspect, a fault-isolation apparatus in a personal computer comprises a power supply having a PSE input, a PSG output and a fault detector coupled to the PSG output; an indicator coupled to the PSG output; and an ON/OFF control. A power supply enabling circuit has a plurality of inputs, one of which is coupled to the ON/OFF control, and has an output for providing an enabling signal to the PSE input of the power supply. The apparatus also includes means coupled to the PSE input of the power supply for simulating an enabling signal.
In a further aspect, for use in a personal computer that includes an ON/OFF control and that includes an enabling circuit having a plurality of inputs, at least one of which inputs is coupled to the ON/OFF control, and having an output for providing an enabling signal, a power supply comprises a PSE input coupled to the enabling circuit; a fault detector; a PSG output coupled to the fault detector; and testing means coupled to the PSE input of the power supply for simulating an enabling signal.
In an additional aspect, a personal computer comprises a system board; a connector that is coupled to the system board and that has a plurality of contacts; an ON/OFF control coupled to a connector contact; a power supply having a PSE input, a PSG output and a fault detector coupled to the PSG output; and an indicator coupled to the PSG output. A power supply enabling circuit is disposed on the systems board and has a plurality of inputs, one of which is coupled through a connector contact to the ON/OFF control, and has an output for providing an enabling signal through a connector contact to the PSE input of the power supply. Also includes is means coupled through a connector contact to the PSE input of the power supply for simulating an enabling signal.